This invention relates to travelling wave or like tubes in which an output lead is required to provide input to a waveguide. In the case of a travelling wave tube having a delay line in the form of a helix, the said output lead is usually a lead attached to or formed as an extension of said helix.
A typical arrangement including a travelling wave tube as above mentioned is illustrated in FIG. 1 of the accompanying drawings.
Referring to FIG. 1 this shows in section the travelling wave tube 1 connected to provide input to a waveguide 2. The helix of the tube is referenced 3. The helix 3 is shown supported by support rods 4.
The end of the helix 3 is connected to an output lead 5 which extends into a tubular output arm 6, forming part of the main body of the travelling wave tube. Output lead 5 is connected to a stepped leadout 7 which extends into window section 8.
One end 9 of window section 8 fits inside the output arm 6, the two being fixed one to the other, in gas-tight fashion, by brazing or the like.
The other end 10 of window section 8, an enlarged end as may be seen, is closed by a ceramic window 11 having a centrally located hole 12 therein. Ceramic window 11 extends it will be noted, transversely to the longitudinal axis of window section 8, stepped leadout 7, output arm 6, and output lead 5. The outer portion of window 11 stands proud of the outer surface of the end 10 of window section 8.
The end 13 of the stepped output leadout 7 is reduced in order to receive one end of a tubular probe 14 forming part of an intermediate connection section 15 which is between the travelling wave tube proper and the waveguide 2.
Thus the travelling wave tube proper consists of all component parts and features referenced 1 to 13 inclusive, so that the output end of the tube comprises the window 11 set within the enlarged end 10 of window section 8, with the reduced end 13 of tapered leadout 7 ready to receive the end of tubular probe 14 through the hole 12 in the window 11.
Intermediate connection section 15 has one end 16 enlarged and shaped to receive the outer portion of ceramic window 11 standing proud of the end 10 of window section 8. End 10 is secured to the window 11 in gas tight fashion.
The other end 17 of the intermediate connection member 15 is formed as a flange by means of which the member 15 is secured to waveguide 2. This flange surrounds an entry hole 18 in the wall of waveguide 2, through which hole the aforementioned tubular probe 14 passes. The end of tubular probe 14 within waveguide 2 enters a ridge 19 provided on the wall of waveguide 2 opposite the wall thereof in which is provided entry hole 18. The ridge 19 provides for matching and includes match adjusting screws 20. Beyond the ridge 19 and almost immediately after the entry hole 18, waveguide 2 is closed by a short circuiting member 21.
The above described construction of travelling wave tube and travelling wave tube arrangement results in a number of disadvantages. For example the tube tends to be relatively fragile particularly in the region of the windows 11 and particularly when designed for higher frequencies. Furthermore the heat transference properties tend to be unsatisfactory.